I. Field of the Invention
This invention relates to whipstocks for diverting the direction of drilling in a wellbore and, in particular, to a retrieval tool for a retrievable whipstock which may be hydraulically set within the well and mechanically retrieved once the drilling procedure is completed.
II. Description of the Prior Art
As drilling procedures have become increasingly sophisticated, the drilling of wellbores which deviate from the vertical or main wellbore has become more critical. Such direction changes can be a result of a course correction or the desire to explore different stratas of the geological formation. It has long been recognized that the simplest method of altering the wellbore was by positively directing the drilling tool in an alternative direction using a whipstock. Early whipstocks were simply placed at the bottom of the main wellbore where subsequent drilling operations would be diverted along the whip face. These early whipstocks may also have been anchored mechanically to ensure proper orientation of the whip face. However, no attempts were made to retrieve these whipstocks and they were typically abandoned in the well. As technology improved it became desirable to set the whipstock in the wellbore at specific positions above the bottom of the hole. Separate packers were first positioned in the well and the whip speared into the set packer. One-trip whipstocks were later developed which allowed the whip to be hydraulically set within the well and the casing milled in a single trip of the drill string. However, much like the early whips, once the wellbore was deviated, the whipstock would be abandoned in the well.